Sounding-board.



F. PRANKEL. SOUNDING BOARD.

APPLICATION FILED SEPT. so, 1911.

Patented May 20, 191.3

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ll/jin'egis'esl. I v I ven/Zora UNTTED STATES PATENT OFFICE.

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' spense-anos of Lettere raient. Application filed SeptemberSU, 1911.Seal No'. 652,124.

Patented May 2o, 191e.

To' all whom t may concern.'

Be it known that I, FRIDOLF FRANKEL, a subject of the King of Sweden,residing at Stockholm, in the Kingdom of Sweden, have 5 invented new anduseful -Improvements in Sounding-Boards, of which the following is aspecification, reference being had to the drawing accompanying hereof.

and forming a part This invention relates td the manufacturing ofsounding-boards for pianos and other g ciently well secured to the frameand suitably stretched therein. It is'to be observed that, in order toobtain a good resonance, it is indispensable that the sounding-board'hasa certain high tension. l

In attachingV sounding-boards te their frames several mistakes have beencommitted. The frames were usually formed by "two extended metal ringsbetween which the sutliciently heated sheet-metal plate was placed. Theplate was thereupon while hot clamped in position by screws. extendingthrough holes in the rings and the plate. It

has, however, been found that, when the tension is very high, the screwscannot sufficiently clamp the plate but allow it to slip.

, Moreover, the rings, as usually constructed, 40 were too weak towithstand the tension, and, therefore, were distorted or caused'toyield.'

The fastening of the plate in a heated condition, in order to obtain asufticienttension by the contraction of the plate in cooling, is

connected with diiiiculties, for as soon as the heat-ed plate is broughtinto contact with the cold metal rings, the edge of the plate is cooledand contracts. y The inner part of the plate is, therefore, caused tobelly and the tension arising as the plate cools is not sufficient tofully stretch the plate. The tension obtained is too small and soirregularly distributed that a good resonance will not be obtained.

The object of the invention is to remove the said drawbacks and make itpossible to Y obtain perfectly goodsoundingboards of sheet-metal. g

Onev part of the invention consists in this that the' plate is slitted'or cut .at the 4edge so that 'a'series of tongues are'formed which.

are fastened vto the frame suitably by bein able way, such asby'bending. vthetongues l around a downwardly projectingiange, by'

' screws, or by a band placed while hot around the tongues atthe outerside ofthefframe'.

exposing the sounding-board secured to' the g Another part of theinvention consists in:

bent over `the outer edge of the'jsame an thereupon secured to the frameany 'sut' frame' to normal pressure, at or inear the bearing surface ofthe frameilsoas to force the sheet metal plate' out ofte plane ofthebearing surface. This method of stretching i the sounding-board4 may be`used'eitherin 'combination with the method ofi/fastening l'ithereinbefore described of the said method.

or independently V The invention furtherconsists in the construction andcombination Aof parts hereinafter set forth.

The new method may be carried into effect in several ways, someof whichwill be described with referen'ce to the drawing.

'r igure 1 is a vertical fragmentary section through the end arts of ayframe having a plate attached to it in the manner setgforth.

Fig. 2 is a plan-view, on a reduced scale'from that of Fig. l, of they slitted plate.t Fig. 3.

is a plan-view of the rame. l Figs. 4: to 9 show modifications.

Referring to the drawing-,the 4frame l is suitably provided with'a stayor stays. (Fig.

3) for strengthening it.i ,Theplate used for the sounding-board-isslitted at the edge, as

shown at l (Fig. 2), so that a series o f.

tongues 5 are formed by'means of. which the plate may be attached to theframe` According to Fig. l, the tongues' ,ofthe plate" are` bentover theedge of the frame '1 and beneath a rim 6 at, the outer side thereof andfurther about a downwardly projecting flange 7 of the frame. f

.In the modified form shown in Fig. 4 the tongues 5, as before, are bentover the edge and catch under the rim 6 of the frame, but instead ofbeing then bent around the lower part of the frame they are securedthereto by screws 8. The modification shown in Fig. 5 differs from theformer in this that the ends vof the ton es 5 are jammed against an edgeor ange 9. y 'In all thev frames shown the outer edge of the framearound which the 'st-rips or tongues 5 are bent-is at. a higher levelthan 'the inner edge l1. The sheet-metal strips or tongues may be stillfurther stretched by means of screws l2 against the said inner edge 1l',as

indicated by dashed and dotted linesl in Fig# l. Between the edges 10-and 114 is suitably a recess or depression allowing the tongues to beforced below the edge 11l by which the tension is still moreincreased.By tighten.- ing the screws l2, after the plate 3 has been fastened tothe frame, the plate will be stretched vto a certain extent before thetongues will bear on the edge 1l, and when the screws are furthertightened, the tongues are bent down into the recess or cavity betweenthe edges l0 and ll so that the sheetmetal plate is strongly stretchedand the desired resonance is obtained. rlhedesired highvtension of theplate may also be obtained by otherwise causingthe plate to ex- 'tendover a longer .way than the plane through the outer edge of the frame.vThis may be performed for inst-ance by screws 13 (Fig. 6) screwed intothe frame from its rear side so as to lift the plate above the level ofthe outer edge. To the same end a nut 14 (Fig. 7) l operated by a screwmay be placed between the plate and the frame.

According to the embodimentsof the invention shown 1n Figs. 8 and 9, thetongues 5 are bent around the frame, whereupon a heated metal strip l5is placedaroundthef tongues so as to clamp the same when it cools. Theouter side of the frame may extend obliquely (Fig. 8) or at right anglesto the plane of the frame.

The stretching devicesv hereinbefore described permit, if desired, tostretch the sounding-board harder at the part-s of the same next to thetreble parts of the piano, which is effected by simply tightening thescrews harder at the said parts. have found that an extremely excellentinstrument is obtained, if the sounding-board' is stretched harder atthe treble than at the bass or the intermediate parts. If the tonguesformed at the edge of the soundingboard are sufficientlyY stiff, eitherby themselves or by suitable reinforcement, the fastening of thesounding-board may be effected by -simply bending the tongues over *theouter edge of the frame, without'any other fastening means beingemployed,

l. ln musical instruments, the combination of a sounding board, a frame,a sheetmetal plate resting on and secured to the frame, and screwsforcing the sheet metal plate out of the plane of the bearing surface ofthe frame, substantially as and for the purpose set forth.

2. in musical instruments, the combinationof a sounding-board', a frame,a sheetmetal plate having a slitted edge extending beyond the outer edgeof the frame and secured thereto, and screws forcing the sheetmetalplate out of the plane of said edges, substantially as and for thepurpose setforth.

3. ln musical instruments, the Combination of a sounding-board, a framehaving an outer edge and an inner edge extending' at a lower level thanthe outer one, a sheetmetal plate having a slitted edge extending framebetween the outer edge and the inner one and forcing the sheet-metalplate' against the inner edge of the frame.

4. .ln musical. instruments the combination of a sounding-board, a framehaving an outer edge and an inner edge extending at a lower level thanthe outer one and separated from the latter by a recess 1n the frame, asheet-metal plate having a slitted edge extending beyond the outer edgeof the frame and secured thereto, and screws placed in the frame betweenthe outer edge and the inner one and forcing the sheetmetal plateagainstthe inner edge of the frame.

FRIDOLF FRANKEL.

lVitnesses Ano. SnnNSuN, KARL lluNcsKoo.

